一种新型低值宽带无感分流器时间常数测量方法

高压脉冲或电力系统中的高频谐波通常采用宽带无感分流器记录瞬态电流波形。分流器的带宽取决于其时间常数, 进而可用于评定其引入的测量不确定度。利用高精度数字多用表测量得到分流器的直流电阻, 通过同步采样方波输入电压以及被测分流器两端的输出电压, 利用最小二乘拟合算法直接计算得到被测分流器的残余电感, 据此确定分流器的时间常数。同步采样采用2根等长电缆与信号发生器的输出进行连接, 避免了信号的传输时延。研究了阻抗匹配对电缆电阻所造成的方波电压和分流器输入端电压差异的影响。结果表明该测量方法可以直接测量阻值1Ω以下、带宽10MHz以下低值无感分流器的电感与时间常数, 成功地解决了宽频电流传感器及宽带无感分流器量值溯源难题。

A New Method for the Measurement of Time Constant of Low Value Wide Band Non-inductance Current Shunt

Wide band non-inductance current shunt was widely used in the field of high voltage impulse and high frequency harmonic of the electrical system. The bandwidth of the current shunt was depended on its time constant which contribute to the measurement uncertainty evaluation. The current shunt time constant was determined by least square fitting method to calculate the inductance of current shunt. A high precision multi-meter was employed to measure DC resistance of current shunt. The input of square wave and the output voltage of the current shunt were measured by synchronized digital sampling. Two equivalent cables were connected to the output of signal generator in order to minimize time delay, the influence of impedance matching on the difference between square wave voltage caused by cable resistance and the input terminal voltage of shunt was studied. The result showed that the proposed method can be used to directly measure the inductance and time constant of the low value non-inductance current shunt with resistance value below 1Ω and bandwidth below 10MHz. The traceability problem of wide frequency current sensor and the wide bandwidth non-inductance current shunt was successfully solved with the proposed method.